1. Field of the Invention
The present invention relates to a solder joint structure and a solder joining method.
2. Description of the Related Art
Soldering is often used for joining a conducting wire made of copper. JP-A 2008-148533 describes a technique of using a copper-coated aluminum wire to solder a conducting wire whose main portion is made of aluminum with a condition similar to that in the case where soldering of a conventional conducting wire made of copper is carried out. In addition, soldering of a conducting wire made of aluminum has been attempted. JP-A 2011-222406 discloses a technique regarding an aluminum-coated electric wire in which a core wire made up of a plurality of aluminum element wires stranded together is coated with an insulating coating. This technique enables a solder to penetrate into the core wire. According to the technique, a portion of the insulating coating is removed from one end of the aluminum-coated electric wire to expose a portion of the core wire thereat, the end of the aluminum-coated electric wire is immersed in a molten solder, and ultrasonic vibrations are applied to the molten solder. In addition, an air inside the insulating coating of the aluminum-coated electric wire is sucked through another end of the aluminum-coated electric wire.
As a method of joining two conducting wires to each other in wiring for an electrical appliance, such as a motor, the following method is sometimes adopted. That is, one of the conducting wires is once joined to a metal pin or the like, and then the other conducting wire is joined to the same metal pin. In the case where this method is adopted, conducting wires made of copper have been used so far. The present inventor attempted to use an aluminum wire as one of the above conducting wires in the above joint structure. JP-A 2011-222406, however, only discloses the technique for enabling the solder to penetrate into the core wire, i.e., a stranded wire, and does not disclose a technique for joining the aluminum wire to the metal pin. Accordingly, the present inventor needed to independently research and develop a joint structure and a joining method to be used when the aluminum wire is joined to the metal pin.